Audio mixing

Abstract

The invention relates to a method and an apparatus for mixing audio signals. The invention is based on the idea to base selection of what audio channels to mix on the dynamic behaviour of the audio channels in terms of whether they are active or not, rather than basing the selection on quantative measures of the audio channels. According to the invention, a set of audio channels are arranged in a mixing stack and a mixed audio signal is produced from the topmost channels above a predetermined threshold level in the stack. Whenever a channel becomes active, it is placed at the top of the stack.

Description

TECHNICAL FIELD OF THE INVENTION [0001] The present invention relates to a method of mixing audio signals and an audio mixing apparatus designed to operate in accordance with such a method. TECHNICAL BACKGROUND AND PRIOR ART [0002] In an audio conferencing system, several participants are connected to a conference bridge. The conference bridge will handle admission control of participants, conference control functions etc. When an audio conference is ongoing, the conference bridge performs media processing in order to receive audio signals from the participants, mix the audio signals to a total signal that will be transmitted to the participants (with the exception that its own signal will be subtracted to avoid echo). [0003] In general, a conferencing system should be scalable, i.e. the hardware that runs the conference bridges should be able to handle several conferences and a great number of participants at the same time. The usual behavior in an audio conference is however that ...

AI Technical Summary

Benefits of technology

[0015] Another advantage of the present invention is that annoying switching behaviour in the background noise in some situations will be avoided. In a situation when a channel changes from active to inactive, and there are not enough active channels to “push” that inactive channel below the threshold level, i.e. there are currently less active channels than the number of channels to mix, the background noise of the channel that just became inactive will still be part of the mixed the audio sources etc. Thus, the present invention should not be interpreted as being limited to speech conference systems or to speech channels.

Problems solved by technology

This saves complexity both in mixing and encoding.

This is because mixing of too many channels, of which some only contain background noise, will degrade quality, as it will degrade the signal to noise ratio of the resulting mixed signal.

One problem with this prior art is the difficulty for a new audio stream to be included in the mix of audio streams.

Another problem with the above described prior art is that such a scheme for mixing audio streams in certain common situations will result in an annoying switching behaviour in the background noise.

This problem will be output signal.

This in turn will result in annoying switching behaviour in the background noise of the mixed output signal.

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